1. Field of the Invention
The present invention is directed to testing, and in particular to testing the function of a mobile station.
2. Brief Description of Related Developments
Up to the digital, cellular systems of the second generation, radio apparatuses, such as mobile stations, have been primarily phones, wherein the information to be transmitted has been primarily digitized speech. For speech transmission in communication between a mobile station and a base transceiver station, a so-called traffic channel has been defined, whose properties are optimized according to features characteristic to speech communication. However, the use of mobile stations is becoming more versatile with expansions in the systems of the second generation and particularly with the introduction of digital cellular radio systems of the third generation. Good examples of expansions of the second generation designed for the GSM system (Global System for Mobile Telecommunications) are HSCSD (High Speed Circuit Switched Data), in which one connection between a terminal device and a base station is allocated several time slots of the TDMA frame; the GPRS (General Packet Radio System) which is based on packet-switched connections between the base station and the terminal device instead of previous circuit-switched connections; as well as the EDGE (Enhanced Data rates for GSM Evolution), in which modulation methods and channel coding are changed to achieve a considerably higher momentary data transmission rate between the base station and the terminal device than in devices of prior art. The GSM system refers generally to its different versions at operational frequencies of 900 Mhz, 1800 Mhz and 1900 Mhz, although the latter ones have also been called DCS1800 and DCS1900 (Digital Communications System at 1800/1900 Mhz).
In more versatile mobile communication, the transmission of data other than digitized speech will be of increasing importance. Data transmission is thus characterized by the non-real-time quality in general, as well as by entirely different demands on error correction and variations in the data transmission rate than in digitized speech. Data transmission comes into question particularly when the terminal device in the cellular radio system is a mobile phone which is connected to a separate data processing auxiliary device, such as a computer. For data transmission, mobile communication systems are provided with specified traffic channels whose properties can be optimized for data transmission.
Testing of terminal devices for the functions involved in e.g. the use of traffic channels has proved problematic. The use of traffic channels is conventionally involved in a situation shown in FIG. 1, in which a mobile phone MS (mobile station) used as the terminal device is locally connected with DTE (data terminal equipment) of a terminal adapter TA. The cellular radio system is simulated during the test by a system called SS (simulation system). The testing of traffic channels has required that a functioning data transmission connection is set up between the SS and the DTE via the MS, to serve a simultaneously functioning application requiring data transmission. The application in question must be active in the DTE and it must be simulated in the SS, which causes extra complication in the test. This may also extend the time duration of the test.
The need of a separate data terminal and the application to be run therein, as well as the very long extended testing time have easily the result that the data terminal interrupts the data transmission connection set up for the test, because one of the time limits specific for the application in question expires or the number of errors detected in the data transmission channel exceeds a limit value specific for the application in question. This causes uncertainty and a need to test the status of the device, particularly the data transmission protocol, during the test. Furthermore, known tests usually apply the procedure that a frame received by the data terminal from the SS (downlink, i.e. data transmission from the base station to the mobile station), is circulated bit by bit as such uplink (i.e. data transmission from the mobile station to the base station), and downlink data transmission is circulated back to the SS, which usually confuses the numbering of uplink frames specific for traffic channels, and also causes the data terminal to interupt the data transmission connection. Moreover, problems are caused by the fact that data transmitted on traffic channels may consist of such upper level units which in the radio connection between the base station and the mobile phone must be divided into several bursts in succession or close to each other. Information is transmitted in the channel in radio frequency bursts with limited duration, consisting of a sequence of modulated bits. So that the data terminal could be confirmed of the error-free reception of the information thus transmitted, it must decode a large number of frames and recombine the information contained therein. As a result of all this, testing of the functioning of a traffic channel by a conventional method involves largely the testing of the functioning of the terminal adapter and data terminal connected with the mobile phone and not the functioning of the mobile phone itself. This is inappropriate particularly for tests related to the type approval (TA) of mobile phones.
Attempts have been made to approach the problem related to cutting off of a connection from the point of view of the functioning of the data terminal, i.e. it has been allocated a testing mode, in which normal reactions to the long connection time and the confusion of numbering of the frames are eliminated. However, this does not eliminate the problem that the final result of the test intended for testing the mobile phone depends largely on whether the data terminal and the software controlling its operation function correctly, or partly on whether the upper levels of the data transfer protocol or external connections (e.g. external data interface) of the mobile phone function correctly.
There are known methods in which the necessary functions are defined, whereby downlink data related to the traffic channels to be tested is circulated back uplink in the mobile station so that it is not passed via the external terminal device. It is characteristic for the test loops of the methods that the response generated in the mobile station to a command of a determined protocol level received from the testing apparatus is to generate a traffic channel test loop to circulate downlink data received from the testing apparatus back uplink to the testing apparatus, and the reception of downlink data and the transmission of uplink data is controlled by said protocol level during the testing.
In the methods, the communication protocol controlling the test situation has been modified in a way that for the test mode, only a required connection of a lower protocol level is opened between the mobile station to be tested and the testing apparatus simulating the cellular radio system. The mobile station does not need to be connected with any external data terminal device at all, nor does an actual data call need to be set up in view of the upper protocol layers being aware of the connection set up. The fact that the upper protocol layers are unaware prevents an untimely termination of the connection by a function involved with them. The test data is conveyed downlink from the testing apparatus to the mobile station which circulates applicable parts of the test data back downlink. The test loop is a logical connection to a certain point in a chain of components and functions intended for downlink data processing.
For testing different functions of a mobile station, the method is modified in several embodiments which differ from each other in the xe2x80x9cdepthxe2x80x9d in which the circulation of the test data of the mobile station takes place uplink. The depth refers to the number of components and/or functions through which the downlink test data proceeds in the mobile station before its circulation back uplink. Preferred embodiments include e.g. the circulation of the test data to encryption, modulation and transmission, as well as after reception, demodulation, decryption, and channel decoding to channel coding, encryption, modulation, and transmission.
Primarily for the GSM system but also for the GPRS system, advantageous embodiments have been defined for circulating test data by means of a test loop in the GSM specification 04.14 Version 5.1.0 (1998-10), which is hereby referred to as prior art. Each test loop is activated in the mobile station by sending the mobile station a command to turn on the test loop. In principle, the information bits contained in each burst received by the mobile station on a downlink traffic channel are circulated back to a certain downlink burst. In the GSM system, each burst contains 114 data bits to be circulated, when so-called stealing flag bits are excluded. In the first defined method, the mobile station circulates the data received in a certain downlink time slot to a time slot of an uplink channel, which in the GPRS is the uplink PACCH time slot. In another mechanism, the mobile station circulates the content of as many received downlink time slots as possible uplink according to certain rules in the GPRS system.
According to the description above, the physical layer (Layer 1) of a circuit-switched GSM system has been tested by forming a data transmission connection. Testing has also been possible by forming the test loop in the physical layer, wherein the mobile station reports the received data to the testing apparatus and it has thus been possible to measure e.g. the sensitivity of the mobile station.
With a mobile station according to the GPRS system, however, it is very difficult or even impossible to perform testing of the physical layer in detail, or merely testing of functions in the physical layer of the GPRS system in the manner described above. According to the character of packet-switched GPRS, data transmission, particularly the formation of physical radio waves itself, is activated only when there is some data to be transmitted in the mobile station. The testing method mentioned in the GSM specification differs thus considerably from the normal operation of the GPRS system. By means of test loops, also the dynamic and independent testing of functions of downlink or uplink data transmission is impossible. Tests of prior art are only applicable for the testing of basic functions in the physical layer, i.e. for testing of the sensitivity of the mobile station. It is typical for type approval tests that certain minimum sensitivity is required of the mobile station at low signal levels, which means that the bit error rate (BER) at a certain signal level must not exceed a determined limit value.
In the GSM system, data transmission between communication devices, such as a mobile station and a base station, takes place on one logical radio channel. The packet switched GPRS system (General Packet Radio Service) boosts data transmission, because the same logical radio channel can be used by several different mobile subscribers. Data transmission between the mobile station and the base station takes place only when needed, and the logical radio channel is not reserved for communication between only one mobile station and base station.
The GPRS system typically contains different MAC modes in uplink resource allocation, of which the use of USF (Uplink State Flag) values in received downlink data blocks (dynamic allocation) can be mentioned. In uplink data transmission, the USF value is used to refer to those uplink time slots, in which the mobile station transmits information. The USF value is transmitted continuously in connection with downlink data transmission. Upon measuring the USF sensitivity, the mobile station needs said USF value as well as the capability to report the received USF value to the test apparatus. In addition to the USF, also other variables are known which cannot be measured by known test loops.
Furthermore, test loops of prior art cannot be used to test the operation of a mobile station in different MAC modes, which include the so-called dynamic allocation mode, the extended dynamic allocation mode, and the fixed allocation mode. In the GPRS system, there is considerably more signalling in the physical layer which did not need to be tested before, such as resource requests preceding the transmission of data blocks.
With reference to FIG. 3 and in a normal situation, data originates from an application of the uppermost layer in the communication protocol (application layer 306), and data transmission (reference 308) is not possible so that the function of the lowest layer, i.e. the physical layer, were predictable. For example, it is very difficult to achieve uninterrupted, continuous data transmission. Furthermore, the control of the precise timing of the RLC/MAC functions is thus not possible, although it would be needed in type approval testing.
As shown in FIG. 3, the terms LLC, RLC and MAC refer to layers (protocol layer) of the protocol structure in the communication protocol used in the mobile station MS. The communication protocol and the different layers constitute the protocol means required in the mobile station for processing and generating data received or to be transmitted. The functions of the known RLC/MAC (Radio Link Control/Medium Access Control) layer 301 are needed between the LLC layer (Logical Link Control) 302 and the physical layer 303 of the wireless communication device MS. The LLC layer 302 is subordinate to the known GPRS mobility management functions (GMM/SM) 305, SNDCP (Subnetwork Dependent Convergency Protocol) functions 304 and also short message service functions. The layers are disclosed in more detail in the GSM standard specifications. The MAC is used for allocating radio channels between wireless communication devices as well as for allocating the physical radio channel to a wireless communication device for receiving and transmission according to the need, as well as for the allocation of LLC frames into the physical GSM radio channel. The RLC block takes care of e.g. requesting for resource allocation for packets to be transmitted to the mobile communication network and to be retransmitted over the radio channel. The SNDCP acts as an interface for the PDP (Packet Data Protocol). The SNDCP block compresses the NPDU (Network Protocol Data Units) received and segments them into one or several LLC frames whose length may vary. These LLC frames are segmented further into RLC data blocks. The GMM protocol supports the functions of mobility management of the mobile station, such as logging in and out (GPRS attach, GPRS detach) and activation (PDP Context Activation, PDP Context Deactivation). The lowermost level, i.e. the physical layer 303 takes care of the physical modulation of radio waves and data transmission between the mobile station and the network.
From the point of view of a mobile station manufacturer, the presence of all the layers of the protocol structure is not always preferred solely to make it possible to test the physical layer. Moreover, the DTE should be connected with the mobile station during the testing. Such arrangements are not possible during tests carried out at the state of manufacturing (production testing). Another problem is, as already mentioned above, the involvement of the upper protocol layers in the testing, wherein the testing and results of the physical layer or the RLC/MAC layer are also affected by the function of an upper layer.
In conclusion, it should be stated that present methods for type approval do not provide means for extensive testing of the physical layer and the RLC/MAC layer of the GPRS system, and particularly not for testing of an uplink connection independently.
It is an aim of the present invention to present such a method for testing the function of a mobile station that the testing is related to the function of the mobile station in an intended manner. It is also an aim of the invention to present a mobile station whose function can be tested in the above-described way.
A central principle in the invention is to provide the mobile station with a test mode which can be activated by means of a received message. The test mode is used to control the transmission of data generated in the mobile station, particularly uplink data transmission. By means of the message and the test mode, it is possible to determine and control delays, data to be transmitted, and desired functions.
Thanks to the invention, the testing of the function of the mobile station and the channels can be directed to particularly those components of the mobile station whose functioning is to be confirmed e.g. in connection with type approval of the mobile station. Furthermore, the testing apparatuses can be constructed to be simpler than before, and difficulties caused by the function of a data terminal are avoided in the tests. Moreover, the invention has the advantage that the connection between the testing apparatus and the mobile station to be tested is a typical situation for the functioning of the system. As an additional advantage of the invention, it can be mentioned that testing methods used by different manufacturers will be unified, which improves the reliability of the testing.
The testing method of the invention makes it possible to have independent tests for the physical layer of the mobile station uplink and downlink separately. A particular advantage is that for uplink data transmission, the generation of resource requests can be controlled and activated from the testing apparatus, which is needed particularly for setting up different tests related to type approval. The invention has also the advantage that it makes it possible to control the timing of the RLC/MAC layer in testing, which is also needed for setting up different tests related to type approval.
By means of the invention, the use of the uppermost protocol layers and applications is avoided in testing, wherein the tests can be applied already at the early stages of manufacture of mobile stations to test the functions of the RLC/MAC functions and the physical layer.